The vapor trapping container relates to underground fuel storage tank vapor pressure control, in general, and more specifically, to the containment of vapors as released from a tank during dispenser shutdown. A unique aspect of the present invention is a perforated stem supporting a bag.
As is well known, the motorist refuels his/her vehicle at a service station. The fuel is pumped from an underground tank, by the dispenser, through a hose and nozzle, for filling the vehicle fuel tank. Normally, the vapors generated within the fuel tank, through fueling, are returned through the vapor path of the fuel hose, back to the dispenser, either by the balanced pressure method, or by a pump, and then are returned to the underground storage tank for containment. As the tank truck replenishes the fuel in the underground storage tank, when the vapor pressure within the tank becomes positive, or even excessive, the vapors must be controlled. Normally, during the day, or evening, when fuel is continuously pumped from the underground storage tank, by the dispenser, to replenish vehicles, generally a more negative form of vapor pressure will be located within the underground storage tank. But, in the evening, when vapors begin to generate, less fuel is pumped from the underground tank, the pressure may build up a little more excessively. Hence, unless this vapor pressure is controlled, released to atmosphere, which regulations will not allow, or is burned, which is also not authorized by law, these vapor pressures either will leak, or can become dangerous. But, through usage of the current invention, means, such as a diaphragm type bag, or expandable bag, or simply a bag that can be inflated, can be attached to a vent of the underground storage tank, accumulate the expanding fuel vapor pressures, and hold them in a safe manner, until such time, during the next day, when fuel is continuously pumped from the underground storage tank, and such vapors can be returned therein. Then the vapor pressure storage bag is deflated, during another daily cycle, of the dispensing of fuels from such an underground storage tank. As is well known in the art, such storage tanks are located underground at most, or all, service stations.
Escaped gasoline vapors raise pollution concerns and trigger governmental regulations. Normally, balance type II vapor recovery stations operate at a negative pressure except during closure of the station. A closed station allows the natural formation of vapors from the evaporation of fuel. Small vapor growth occurs during closure of a station. However, vapors may escape to the atmosphere, causing pollution or increase pressure, adversely affecting station operations.
Prior art designs provide vapor collection with refrigeration, membranes, bags, and containers on vents. Though collecting vapors, the prior art required additional mechanical equipment and controls while not returning vapors to their source. The prior art also tends to have higher installation and operational costs.
The present art overcomes the limitations of the prior art. That is, in the art of the present invention, a vapor trapping container retains vapors in an expandable bag and returns the vapors to a confined space at lower pressure without mechanical equipment. In other words, no other vapor paths are required.
The difficulty in providing a vapor trapping container is shown by the operation of a typical vapor recovery system. Hydrocarbon vapors collect in an underground tank or spill. A controlled vacuum device alters the pressure to withdraw the vapors from the tank. The vapors then undergo desiccation and refrigeration in separate machinery from the tank or spill to return and become liquid again. The liquid is then returned to near the bottom of the tank or removed from a spill site. In operation, the typical system requires electrical power and skilled labor to install, to operate, and to maintain the vacuum device, and desiccation and refrigeration processes. The present invention overcomes these difficulties.
The use of containers to capture escaping vapors is known in the prior art. For example, U.S. Pat. No. 2,758,747 to Stevens discloses a multiple compartment tank that conveys different commodities.
The patent to Viland, U.S. Pat. No. 3,763,901, shows a method of preventing loss of hydrocarbons into the atmosphere. This method refrigerates and condenses vapors to liquid and returns the liquid to a tank. This patent covers more of a storage bag with some rigidity rather than an inflatable bag.
The patent to Fischel, U.S. Pat. No. 3,807,396, shows a life support system to recycle gaseous oxygen. The system has multiple vessels and an expansion bag as a water trap.
The patent to Hughes et al., U.S. Pat. No. 3,978,694, shows a vapor saving system for a dry cleaning machine. The system retains dry cleaning solvent vapors when an operator opens a door. An impervious bag in the system collects solvent vapors.
The patent to Harper, U.S. Pat. No. 4,108,160, shows a solar water heating apparatus with an expandable vapor recovery bag. The bag attaches to the vent but the vent does not extend through the length of the bag and lacks perforations.
The patent to Grant, U.S. Pat. No. 5,058,631, shows flexible gas salvage containers for use with refrigerants. Upon filling the bags with recovered refrigerant, an operator removes the bags to a collecting point. No perforated stem extends into the bags.
The next patent to Grant, U.S. Pat. No. 5,176,187, shows a related flexible gas salvage container used in the automotive air conditioning field. This patent defines a refrigerant vapor recovery system that has bags connected to a pump or manifold.
The patent to Furstenberg, U.S. Pat. No. 5,343,908, shows a liquid containment system designed to prevent vapor formation. This system has membranes under pressure and bolted to a base, but lacks a bag shaped component.
The patent to Prescott et al., U.S. Pat. No. 5,655,579, shows a method and apparatus to test a fire suppression system. A bag in this system collects discharged fire suppressant but does not reload the suppressant into the system.
The patent to Leonard, U.S. Pat. No. 6,070,365, shows a domed explosion vent. The vent releases pressure above a certain value from within a building. A panel of the vent deflects to release vapors generated during an explosion.
The patent to Chiu, U.S. Pat. No. 6,553,713, shows a method and device for re-forestation and flood control. The device has a tent housing of flexible material with a sand base to weigh down an individual unit. The housing has openings with check valves to maintain pressure within the housing at or near ambient air pressure. The housing may store water to irrigate plants.
Thus, prior art devices do not provide for a flexible vapor trapping container that retains vapors in response to pressure changes in a storage tank. The flexible vapor trapping container inflates with vapors released from a tank, stores the vapors, returns the vapors and/or condensate to the tank, and deflates until the cycle repeats.